The present disclosure relates to a semiconductor structure and a method of fabricating the same. More particularly, the present disclosure relates to a high programming efficiency electrical fuse (eFuse) structure and a method of fabricating the same.
Electrical fuses (eFuses) are used in the semiconductor industry to implement array redundancy, field programmable arrays, analog component trimming circuits, and chip identification circuits. Once programmed, the programmed state of an electrical fuse does not revert to the original state on its own, that is, the programmed state of the fuse is not reversible. For this reason, electrical fuses are called One-Time-Programmable (OTP) memory elements.
A typical mechanism for programming an electrical fuse is electromigration of a conductive material induced by an applied electrical field and an elevated temperature on a portion of the electrical fuse structure. The conductive material is electromigrated under these conditions from the portion of the electrical fuse structure, thereby increasing the resistance of the electrical fuse structure. The rate and extent of electromigration during programming of an electrical fuse is dependent on the temperature and the current density at the electromigrated portion.
An electrical fuse typically comprises an anode, a cathode, and a fuselink. The fuselink is a narrow strip of a conductive material such as a metal adjoining the anode and cathode, which may also be composed of a metal. During programming of the electrical fuse, a positive voltage bias is applied to the anode and a negative voltage bias is applied to the cathode. As electrical current flows through the fuselink having a narrow cross-sectional area, the temperature of the fuselink is elevated. A high current density combined with the elevated temperature at the fuselink facilitates electromigration of the conductive material. Electromigration, in turn, causes the conductive material to pile up and form hillocks at the anode of the electrical fuse.
In the formation of current electrical metal fuse structures, one of the main problems that is encountered is the requirement of large spaces and a very complex processing operation, particularly involving copper. In addition, metal fuse rules are limited to particular restrictive values. Based on the foregoing, a need exists to reduce the space required in the formation of electrical metal fuses used in integrated circuit devices.